Reconstituted tobacco sheet having a starch phosphate binding agent



United States Patent 3,438,379 RECONSTITUTED TOBACCO SHEET HAVING A STARCH PHOSPHATE BINDING AGENT Frank J. Mitan and Lawrence R. Cohen, Whiting, Ind., assignors to American Maize-Products Company, a corporation of Maine No Drawing. Filed Dec. 28, 1966, Ser. No. 605,229 Int. Cl. A24b 3/14; A24f 47/00 US. Cl. 131-17 4 Claims ABSTRACT OF THE DISCLOSURE A binding agent consisting of phosphate derivatives of starch, defined by the method of preparation thereof, is used in the manufacture of sheets of tobacco from small fragments of tobacco such as particles, shavings and fines, such agent permitting the sheets to be formed mechanically with high strength at ambient temperatures.

ture of cigarettes, cigars, etc. Many attempts at salvaging have involved the forming of sheets from the finely divided tobacco, the objective here being to produce simulated natural leaf tobacco which might then be used for manufacture of additional commercial smoking products. One conventional method for reconstituting has involved high temperature extrusion of a mixture of the tobacco particles and starch, the latter being gelatinized in situ in the extruder. This process is undesirable inasmuch as it discolors the tobacco, causes loss of moisture and tends to degrade the flavor of the tobacco due to roasting of the tars and gums which are naturally contained therein.

Another conventional method of reconstituting has involved the forming of sheets by mechanical means at lower temperatures wherein the tobacco particles are combined with some form of adhesive in a slurry which is spread in a layer and then dewatered to form a sheet. Here again, this conventional process has drawbacks inasmuch as such sheets are usually markedly deficient in wet strength and also the natural gums of the tobacco are leached out by the dewatering step.

In accordance with the present invention, it has been found that certain starch derivatives in the nature of phosphate esters of starch, when used as the sole or principal binding agent in reconstituted mechanically formed tobacco sheets, impart greatly increased strength to the final sheets as measured by increased bursting strength and wet and dry tensile strengths. The magnitude of improvement is very large inasmuch as the bursting strength may be increased by about 200 to 400%, the dry tensile strength by about 75% and the wet tensile strength by about 25 to 50%. Thus, tobacco sheets formed in accordance with the invention have much more value for use as simulated natural leaf tobacco in cigars, cigarettes and other smoking products. For example, because of their much higher strength, tobacco sheets formed in accordance with the invention can be used as secure outer wrapper for cigars having good appearance, flavor, resistance to tearing and burning characteristics.

The substantial improvement in strength provided by the binding agent of the invention is all the more surprising inasmuch as related starch products have been tested and found to be incapable of giving the same benefits. For exice ample, ordinary common starch, high amylose starch, high amylopectin (waxy maize) starch, hydroxyethyl and hydroxypropyl ethers of high amylose starch, hydroxyethyl ether of high amylopectin starch, dialdehyde starch and oxidized starch have all been used as binding agents in tobacco sheets and none of these could approach or duplicate the tremendous improvement in strength that distinguishes the starch phosphate binding agent of the invention. Thus, actual tests show conclusively that the starch phosphate derivative has, for reasons which are not entire ly understood, unique eflicacy for binding tobacco particles in the manufacture of self-supporting tobacco sheets even though other related starch materials give unacceptable results.

In addition to the benefit of increased strength, the starch phosphate binding agent of the invention provides additional advantages due to the fact that it is cold water soluble. This means that the starch phosphate binding agent can be incorporated in tobacco sheets in a mechanical Fourdrinier type sheet-forming process without having to apply heat or raise the temperature above ambient temperatures. As a result, naturally contained gums in the tobacco are not lost to any substantial degree by leaching the tendency for which is very much intensified by elevation of temperature as is required in use of certain conventional tobacco binding agents in Fourdrinier type processes. The naturally contained gums contribute to the flavor and burning characteristics of tobacco and such characteristics are not adversely affected in use of the starch phosphate binding agent of the present invention.

The starch phosphate derivatives to be used in accordance with the invention are complex reaction products of starch and at least one alkali metal phosphate salt, and while the molecular structure is not entirely understood, the products are considered to be orthophosphate esters of starch, the hydroxyl groups thereof being the points of attachment for the bound phosphate groups. These starch phosphate derivatives are produced under controlled reaction procedures which in essence comprise impregnating ungelatinized starch granules with at least one alkali metal phosphate salt dissolved or dispersed in water or some such liquid carrier, this impregnation being effected without gelatinization of the starch granules, then separating the starch granules from any unabsorbed portion of the phosphate salt solution or dispersion, reducing the moisture content of the starch granules to 20% by weight or less and finally roasting the partially dried granules at temperatures from about to about C. to react the starch with the impregnated, absorbed phosphate, salt therein. Such reaction products are sometimes referred to in the art as Neukom starch phosphates and further details regarding their preparation are found in US. Patents 2,884,412; 2,884,413 and 2,993,041.

For use as tobacco binding agents in accordance with the present invention, it is necessary that the starch phosphate derivatives have a final chemically bound phosphate content of from 0.1 to 10% based on the weight of the derivative. Such reaction products will give a variation in binding power over a range which will be useful for virtually all species of tobacco to be reconstituted in sheets as regards the genetic origin and the particular physical form of the tobacco. In more commercial embodiments of the invention, it is preferred to use starch phosphate derivatives having a bound phosphate content from about 0.5 to about 5.0% based on the weight of the derivative. The phosphate contents given in the specification and claims herein are in terms of percent P0 based on the weight of the starch phosphate derivative.

As for the amount of starch phosphate binding agent required, it has been found that use of from about 0.5% to about 10% of the starch phosphate based on the Weight of the tobacco to be reconstituted will give beneficial results in improving the strength of the final reconstituted sheet. Particularly notable increases inbursting strength and wet and dry tensile strengths have been achieved with use of about 2% to about 7% of starch phosphate derivative based on the weight of tobacco and these amounts are preferred for optimum results.

The starch phosphate binding agent is added to a slurry of the tobacco particles that are to be reconstituted and then the slurry is sheeted out into the form of a loose mat or blanket as by use of Fourdinier wire screens or equivalent mechanical means. Water is next removed from the sheeted tobacco as by suction or application of positive pressure and then the dewatered sheet is dried and stabilized, preferably by air drying at room temperature of 73 F. and controlled 50% relative humidity.

As previously noted, it is a distinct feature and advantage of the present invention that the starch phosphate binding agent may be thoroughly dispersed and dissolved in the tobacco slurry without application of heat, whereby the tendency for leaching out desirable natural constituents of the tobacco is minimized.

The starch phosphate may be added directly to the tobacco slurry in which case the slurry is mechanically agitated to disperse and dissolve the added starch phosphate before the slurry is formed into a sheet. Alternatively, the starch phosphate may be first dispersed or dissolved in water and then added to the tobacco slurry in the form of the resulting aqueous solution or dispersion whereby less mixing time and agitation will be required to form a uniform tobacco slurry With the added starch phosphate binder. Also, heat may be applied to the preformed starch phosphate-water mixture or solution followed by cooling thereof before addition to the tobacco slurry in order to shorten the processing time without adversely affecting the quality of the tobacco. While heating of the tobacco slurry in general should be avoided, in some specific cases application of mild heat may be desirable as a processing aid and such use of heat is therefore within the scope of the present invention.

In addition to the starch phosphate binding agent, other auxiliary ingredients may be added to the tobacco slurry. For example, hydrophilic plasticizers such as polyols including glycerol, glycerol esters, ethylene and propylene glycol, polyethylene and polypropylene glycols and ethers and esters thereof, sorbitol and corn syrups may be added to impart flexibility and moisture retention characteristics to the final reconstituted tobacco sheet. Such ingredients are optional and may or may not be considered desirable depending on factors such as the particular species of tobacco particles to be reconstituted, the humidity and temperature in the area where the reconstituted tobacco is to be used and phosphate content of the particular starch phosphate reaction product to be used as the finding agent. When plasticizers are used, the total amount thereof may be from 1 to 15% based on the weight of tobacco in the reconstituted sheet.

Further details of the present invention will be readily understood from the following examples which constitute several specific embodiments thereof.

4 EXAMPLE 1 Into a pound laboratory size Valley beater machine were placed 360 grams of tobacco fines, 300 milliliters of propylene glycol and 15 0 millilters of glycerine. Water was added to these ingredients to form a slurry of 23 liters total volume. The slurry was refined by operation of the beater for a period of 12 minutes with a weight of 5500 grams on the beater roll. Samples of the refined slurry were taken from the beater and used to prepare reconstituted tobacco sheets containing three different binder additives.

One of the additives consisted of a dialdehyde starch having a 54% aldehyde content (hereafter designated additive A). The second additive consisted of an hydroxypropyl ether of a special genetic species of starch having a natural amylose content above 50% by weight (hereafter designated additive B). The third additive consisted of a starch phosphate derivative prepared in accordance with the method previously described hereinabove, and having a bound phosphate content of about 3% by weight (hereafter designated additive C).

Aqueous dispersions of the three additives A, B, C were prepared and added to portions of the refined tobacco slurry in the preparation of molded test sheets. Each sheet was formed with 4 grams of tobacco (in the slurry thereof) and an appropriate quantity of the additive dispersions to give varying concentrations of additive relative to the weight of tobacco. The specific method used to prepare the sheet test samples was TAPPI, Testing Method for Hand Sheet Mold Process, T-205-M-58, as specified by the Technical Association of the Pulp and Paper Industry (TAPPI) of New York, NY. The newly prepared sheet samples were allowed to air dry at 73 F. and 50% relative humidity overnight prior to testing.

Additive A was formed into three different mixtures with additive B wherein the respective relative weight proportions were 75% A-25% B, 50% A50% B and 25% A-75% B, all three mixtures being used in an amount comprising 18% of total additive based on the weight of tobacco in the sheet. Additive B was used alone in amounts of 1 to 10% of additive based on tobacco weight. Additive C was used alone in amounts of 1 to 7% of additive based on tobacco weight. Blank sheet samples were also prepared by the same procedures in each additive test series without incorporating any of the additives A, B and C.

The various sheet samples were tested for bursting strength and for dry and wet tensile strength. The bursting strength was measured using the method TAPPI, Bursting Strength Procedure, T-=3-M53. The dry and wet tensile strengths were determined using the respective methods TAPPI, Dry Tensile Procedure, T-404- OS61 and TAPPI, Wet Tensile Procedure, T-456-M 49. The basis weight of each sheet, both actual and corrected for moisture content, was determined by TAPPI, Weight of Hand Sheets Procedure, T4-10-OS-61. The moisture content in each sheet was determined by the method TAPP I, Moisture of Handsheets, T2.10M-58. The results of these tests are recorded in the following tables:

TABLE I.ADDITIVES A AND B MIXED Basis weight Bursting Dry tensile Sample (grams/me- Percent Dryness Corrected strength breaking ters moisture factor basis weight (p.s.i.) length (meters) Blank 206. 9. 0 91 187. 92 1. 310 581 18% A25% B) 224. 00 9.0 91 203. 84 0.950 223 18% (50% A-50% B 258.75 9. 0 91 235. 46 0.523 398 18% (25% A75% B) 244. 50 9. 0 91 222. 50 0.760 349 TABLE II.ADDITIVE B ALONE Basis weight Bursting Dry tensile Sample (grams/me- Percent Dryness Corrected strength breaking ters moisture factor basis weight (p.s.i.) length ((meters TABLE III.-ADDITIVE C ALONE Basis weight Corrected Bursting Dry tensile Wet tensile Sample (grams! Percent Dryness basis breaking breaking breaking meter moisture factor weight strength length length (p.s.i.) (meters) (meters) Comparison of the foregoing tables demonstrates that additives A and B were incapable of improving the cate results that were obtained with duplicate samples in each case:

TABLE IV.--STARCH PHOSPHATE (SP) ALONE Basis weight Corrected Bursting Dry tensile Wet tensile Sample (grams! Percent Dryness basis breaking breaking breaking meter moisture factor weight strength length length (p.s.i.) (meters) (meters) strength of the blank reconstituted tobacco sheets and instead the strength was seriously weakened. In contrast, additive C comprising the starch phosphate binding agent of the present invention imparted a substantial improvement to the strength characteristics of the blank tobacco sheet.

EXAMPLE 2 Test samples of reconstituted tobacco sheets were prepared by the methods described in Example 1 and evaluated for strength characteristics. In this example, the samples included a blank and a series of samples containing a starch phosphate binding agent in amounts varying from 3% to 6% based on the weight of tobacco in the sheet. The starch phosphate derivative was prepared by the method previously described hereinabove and had a bound phosphate content of about 3%. Both the preparation and testing of the samples were done by the TAPPI procedures in Example 1.

The results of the tests in this example are recorded in the following table, the entries being an average of dupli- The foregoing table demonstrates again that the starch phosphate binding agent of the present invention gives a very substantial improvement in the strength characteristics of reconstituted tobacco sheets.

EXAMPLE 3 In this example, the effect of the hardness of the water used to form reconstituted tobacco sheets was evaluated as against the efficacy of the starch phosphate binding agent of the invention. Two ditferent series of test samples were prepared the first being carried out with pure distilled water, the second with simulated hard water containing 200 ppm. of calcium carbonate. In both series, a blank tobacco sheet was prepared and two more sheets containing respectively 3% and 6% of the starch phosphate binding agent tested in Example 2, these amounts of the starch phosphate again being based on the weight of tobacco. The preparation and testing of these samples were carried out by the TAPPI procedures identified in Example 1 and the results of these tests are recorded in the following table:

TABLE V.STARCH PHOSPHATE (SP) ALONE Basis weight Bursting Dry tensile Wet tensile Sample (grarns/ Percent Dryness Corrected strength breaking breaking meter moisture factor basis weight (p.s.i.) length length (meters) (meters) As will be noted, the presence of a large amount of calcium carbonate has no adverse effect upon the improved strength achieved by use of starch phosphate binding agents in accordance with the invention.

It will be understood that it is intended to cover all changes and modifications of the preferred embodiments of the invention, herein chosen for the purpose of illustration, which do not constitute departures from the spirit and scope of the invention.

What is claimed is:

1. An improved tobacco product comprising a self-supporting tobacco sheet containing finely divided tobacco and a starch phosphate derivative having a bound phosphate content of about 0.1% to about 10% based on the weight of said derivative, said derivative having been prepared by impregnating starch granules with an aqueous solution of at least one alkali metal phosphate salt, then separating the granules from any excess salt solution not absorbed by the granules and then roasting the separated starch granules at temperatures from about 100 C. to about 175 C. and wherein the amount of said starch phosphate derivative is from about 0.5% to about 10% based on the weight of tobacco in said sheet.

2. A tobacco product as in claim 1 wherein the bound 8 phosphate content of said starch phosphate derivative is from about 0.5% to about 5%.

3. A tobacco product as in claim 1 wherein the amount of said starch phosphate derivative is from about 2% to about 7% based on the weight of the tobacco in the sheet.

4. A tobacco product as in claim 1 which includes a plasticizer comprising at least one of glycerol, glycerol esters, ethylene glycol, propylene glycol, polyethylene and polypropylene glycols and ethers and esters thereof, sorbitol and corn syrup, the total amount of said plasticizer being from about 1% to about 15% based on the weight of tobacco in said sheet.

References Cited UNITED STATES PATENTS 3,009,835 11/1961 Samfield et al. l3l140X 3,098,492 7/1963 Wurzburg et al 131-140 3,317,514 5/1967 FOX et al. 260--233.5

MELVIN D. REIN, Primary Examiner.

US. Cl. X.R. 13l140 

